1. Field of the Invention
The present invention relates to an electronic device, and in particular to an electronic device using flexible printed circuit boards.
2. Description of the Related Art
Flexible printed circuit boards (FPCB) have been utilized in a variety of electronic devices such as liquid crystal displays (LCDs) for electrical connection. The flexible printed circuit boards are light, bendable, and convenient for assembly, providing a compact profile.
FIG. 1A is a schematic exploded view of a conventional liquid crystal display 100′. FIG. 1B is a schematic front view of the conventional liquid crystal display 100′.
The liquid crystal display 100′ comprises a front bezel 10′, a panel 20′, a flexible printed circuit board of panel 30′, a plurality of optical films 21′, a light source 40′, a flexible printed circuit board of light source 50′, a light guide plate 41′, a reflector 43′, and a rear bezel 60′. The elements 40′, 41′, 42′, 43′ are assembled to form a backlight module.
As shown in FIG. 1A, the panel 20′ is sandwiched between the front and rear bezels 10′ and 60′. The light source 40′ is disposed above the rear bezel 60′. Signals produced from the panel 20′ are transmitted by the flexible printed circuit board of panel 30′ to other interfaces of the liquid crystal display. The flexible printed circuit board of panel 30′ is connected to a side of the panel 20′ and protrudes from the front and rear bezels 10′ and 60′. The protruding portion of the flexible printed circuit board of panel 30′ is an angled portion 32′. During assembly, the angled portion 32′ can be bent 90° or 180° in direction B rearward to connect with other interface.
In addition, direct backlight and edge-light technologies can be employed according to the size of LCD. Here, edge-light technology for small sized LCD is used as an example. A light emitting diode (LED) acting as light source 40′ is connected to the flexible printed circuit board of light source 50′, providing power and transmitting signals.
LED 40′ is small, and the flexible printed circuit board of light source 50′ is narrow, and both are disposed between the panel 20′ and the rear bezel 60′. A portion of the flexible printed circuit board of light source 50′ protrudes from the front bezel 10′ and the rear bezel 60′ after assembly, specifically an angled portion 52′. The angled portion 52′ and the angled portion 32′ are connected and bent 180° to the back of the panel 20′.
The flexible printed circuit boards 30′ and 50′ are welded at connection points 31′ and 51′.
FIG. 1C is a rear view of an assembled conventional LCD 100′ with flexible printed circuit boards 30′ and 50′ are angled together. FIG. 1D is a side view of an assembled conventional LCD 100′ with flexible printed circuit boards 30′ and 50′ are angled together, in which the dashed line represents the original positions of flexible printed circuit boards 30′ and 50′ before bending.
The flexible printed circuit boards 30′ and 50′, of different lengths, are connected and fixed at the connection points 31′ and 51′. When angled, since the thickness of the panel 20′ is about 0.63 mm, the angled portions 32′ and 52′ experience different radii of curvature.
Thus, when bending toward the back of the panel 20′, because the angled portions 32′ and 52′ are fixed at the connection points 31′ and 51′, the flexible printed circuit board of light source 50′ is constrained and surrounded by the flexible printed circuit board of panel 30′ with a larger radius of curvature. It is shown that the flexible printed circuit board of light source 50′ is squeezed into the limited space surrounded by flexible printed circuit board 30′. The flexible printed circuit board 50′ is deformed accordingly.
In addition to deformation, the connection points 31′ and 51′ may be separated by strain and stress on angled portions. If the flexible printed circuit boards are separated during assembly, process is interrupted and materials wasted, increasing assembly time and manufacturing costs.